Spark plug and method of making the same



` June 16, l942 s. H. sTuPAKol-'F SPARK PLUG AND METHOD yOF MAKING THESAME -Filed sept. 11, 1940 Z6 J4 33 )l gemela J7. S'upakoff jupATTORNEY- l INVENTOR y making of the od is the use in special relationtothe glass, of al metal or alloy whose coeilicient of thermal ex.

Patented June is, i942 Semon Il. Stupako, Pittsburgh, Pa., assigner toThe Spark'liing Comration, New

York, N. Y.,

a corporation of Delaware Application September 11, v194:0, Serial No.356,240 18 Claims.' (Cl. 123169) tion pertains is that wherein anelectrode-carry-4 ing main outer metal body or jacket and through whichis extended the central electrode, is separated from the latter by aninsulator made of a material, such as glass, which has a coemcient ofthermal vexpansion lower than the metal of which the jacket is made.

In U. S. patent to me No. 2,103,759, there is disclosed a method ofemploying a material like glass, instead of porcelain or the like, forthe insulator.l A feature of said methpanslon can be matched to glass,such, for instance, as the' alloy Kovar. As explained in my U. 8. PatentNo. 2,103,759 Kovar is an alloy of the type disclosed in U. S. PatentNo. 1,942,260, and this alloy is commercially available under thetrade-mark Kovan The use of a material like glass for the insulator butin a different way than as explained in said patent, and of a metal oralloy like Kovar substantially according t'o. the teachings of saidpatent so far as is concerned the useful functioning of said metaivwhenencircled by glass and when interpody between the jacket and glass, isthe basis of the present invention. (Hereinafter, for brevity, Kovarmerely will be mentioned and claimed, but then as inclusive of Kovar orthe like, that is. of any metal or alloy having a coefficient of thermalexpansion which can be matched to glass; likewise for brevity, glass.merely will be mentioned and claimed, but then as inclusive of anysuitable transparent material. A transparent material for the insulatoris highly desirable,

- for the reason that when the insulator is transparent one candetermine by the light which diffuses upwardly through the insulatorjust how the cylinder is firing without removing the plus from theengine.)

In the-particularway described in detail in said patent as the thenrecommended procedure in carrying out the method forming thesubjectmatter thereof, the glass insulator is a preformed tubular one,and the auxiliary member, made of Kovar, is of ring form'. l In carryingout the present invention, a Kovar member in this form is stillpreferred; but the insulator is a solid mass 'of glassy cast in situ, inthe metal jacket, for instance as taught in U.- S. Patent No. 1,731,280to Warren, and preferably thus cast after preassemand hereinafter also,

bly of the Kovar member and the jacket in such manner that at least apart of said member is extended into the interior of the jacket, so thatthe molten glass entered into the jacket solidiiles in part against themetal of the jacket and in part against a portion of the Kovar member inthe jacket.

Thereby' the very important objects are obtained of effecting a largereduction in the cost of manufacture of a plug made in accordance withthe aforesaid patent to me while retaining important advantages thereof,this because the glass insulator is cast in place in the jacket; and ofproviding mechanically a much sturdier plus, thisr because the insulatoris a solid block of glass instead of a fragile tube.

By the present invention, as in said patent to me, the Kovar member ispreferably non-.integral with the jacket and is permanently fused, as bythermal coefilcient has been successfully used, to provide not onlywelding, to the jacket, so as to set up a permanent gas-tight sealbetween vthe jacket and the Kovar member; but by the present inventionthe Kovar member is preferably wholly contained in the jacket when thus-joined thereto, thereby to have said member completely embedded in` theglass insulator.

In carrying out the present invention, thereby to provide a, solid glassinsulator instead of a tubular one as recommended in said patent to me,a'borosilicated glass having about the same as called for by said patenta gas-tight plug but a very inexpensive and rugged one havingsuillciently high resistance to thermal shock and enough electricalresistance between its jacket and its central electrode to warrant itsadoption in service.

^ The invention will be more clearly understood from the followingdescription, when taken in connection with the accompanying drawing,which illustrates embodiments of the invention.y

as now preferred, but it will be understood that this drawing anddescription are merely by way of illustration, since the scope ofprotection con- I templated ls to be taken from `the claims appended.

Insaid drawing: Fig. 1 shows, in side elevation, one form of largedscale, a Kovar ring member which is in the form of an eyelet.

Fig. is a vertical sectional view, taken through a means for molding theglass insulator.

Fig. 6, partially broken away at the top, is a View similar to Fig. 3,showing a different embodiment.

Fig. 7 is a view similar to Fig. 6, showing still another embodiment.

Referring to the construction illustrated in Figs. 1 through 4, I0designates the metal jacket, having a head portion II polygonally shapedfor engagement by a wrench, and a threaded extension I2 to be entered-ina cylinder of the engine. A central electrode I4 has its main length,this length marked I5' and made of Kovar, ,encased in an insulator IIwhich is a solid mass of glass cast in situ, so as to iill the interiorof the jacket down to a point some distance above the bottom of thelatter, and so as to extend up above the top of the jacket as asubstantially conical extension the flat top of which lies against theunderside of a disk I1 which is integral with a threaded stud I8 fortaking a nut-like terminal I9. i

The central electrode I4 is shown as made up of three separate pieces,these being the said main length I5 of Kovar, an upper iitment includingthe disk I1 and the stud I8v of any suitable metal or alloy lessexpensive than 4Kovar, and a lower sparking tip 20 of any suitable metalor alloy better adapted than Kovar to constitute a sparking point.'I'hese three pieces which here make up the central electrode arepermanently joined into a unitary structure, as by welding the squaredoi upper end of the part |5 to the disk I1, and the squared off lowerend of' the ggrt I5 to the squared off upper end of the tip Any suitabletype of electrode for sparking coaction with the central electrode canbe provided, such as the one shown at 2|, projected from the inner endof the threaded extension I2 of the jacket.

The hollow within the jacket I 0, which extends from end to end thereof,is annularly flatly shouldered at 22, and on this shoulder is seated aKovar eyelet 23.' The eyelet is positioned on the shoulder 22 so thatthe horizontal flange 'of the eyelet rests on said shoulder, and thisfrange is Welded to the shoulder. Since in the form of the invention nowbeing described the entirety of. the eyelet will be embedded in theglass as soon as the insulator is castl in place in the jacket, weldingof the horizontal flange of the eyelet to the shoulder 22 will beperformed before the glass insulator is cast. The welding is continuousall around the eyelet.

Referring to Fig. 5, the jacket I0, .having welded therein the eyelet23, is shown as held in obtained when the glassis flowed into thejacket' `of the plugin a direction such that the glass moves thereinalong a path causing it to be a mold including separable parts 24 and25, es-

tablishingA between them a cavity 26 shaped at its extreme left end toreceive the disc I 1 and the stud is of the centrai electrode u. Theop-L posite endof this cavity is shaped to receive a metal plug 21. Tothe left of the location for this plug, the cavity 28 is shaped toreceive the jacket I0, and to the left of the location for the jacket,the cavity is shaped to form the conical extension of the insulatorbeyond the jacket. The

end of the plug 21 adjacent to the jacket is reduced in diameter to ntsnugly within yet readily removably from the interior of the jacket, andthe plug has an annular shoulder -28 to abut against the inner end ofparts are arranged as illustrated. 'Ihis reduced end of the plug 21 hasa cylindrical recess 29 for seating the sparking end of the centralelectrode I4. The cavity 26 furthermore is so shaped, relative to theshaping of the jacket I0, that with the mold part 24 removed, and withthe plug inserted in the jacketl and the center electrode linserted inthe plug, this temporary assembly of jacket, 'plug andcenter electrodecan be laid in the part of the cavity 26 formed in the mold part 25 insuch way as to insure maintenance of such assembly' and to settle thecenter electrode in the jacket coaxial with the latter and at the sametime in a way to locate a round opening 30 in the jacket, normal to oneof the flat faces of. its

- Wrench-taking vpart I I as indicated in Fig. 1, in 'registry with' amolten glass supply port 3| in patent is owned by the assignee hereof,who is' 'also the assignee of the aforesaid patent to-me.

The molten glass supply port 3| is at the bottom center of a moltenglass feed c up 32, served by a descending" plunger 33 carryingcompression rings 34 and 35. As the parts are shown, this plunger hasdescended just far enough tocause a little of the molten glass tobeginentry into port 3|. Y After setting of the glass, the plug is com',pletely made; except for, preferably, the subsequent'addition of theelectrode 2|, and exceptv for breaking off the stem of glass intheopening 30 where the latter protrudes beyond the exterior of the partII of the jacket, should it so protrude after opening'of the mold andremoval of the plug therefrom, and except for grinding the glass. smoothand flushl with-said part II, if such inish is desired.

Referring to the form of the invention shown in Fig. 6, the plug here4shown is inall respects similar to the plug of Fig. 3, and'is one madeas describe.' in connection with Figs. 3 and 5, except that the Kovareyelet 23 is arranged with its neck depending, instead of upstanding asin Fig. 3. The arrangement of Fig. 6 is preferred over that of Fig. 3,as eliminating or minimizing the creation of small checks in the glass,sometimes struck head-on by an edge portion of the/Kovar member, whichmember is usually 'onlya few thousandths of an inch thick. It is mostconvenient to admit the glass through aport in the' jacket at about thelocation ofthe port 3U of Fig. 1, so that the glass ows in the jackettoward and past the shoulder 22 and whereas in the case of Fig. 3, themolten glass thus admitted moves in a path so as to be struck head-on bythe upper edge portion of the neck of the eyelet, in Fig.y6 the -moltenglass thus admitted moves in a path so as to slip freely pastsaid edgepor- A tion, now at the bottom of the eyelet and close the jacket whenthe against a cylindrical interior of the jacket below the shoulder 22.

The form of the invention shown in Fig. 7

even better attains the advantage last discussed.

Here, it will be noted, with the Kovar member still the eyelet 23, andarranged as in Fig. 6 on.

a shoulder 22' exactly like the shoulder 22 of Fig. 6, the jacket,marked, III', hasitsinterlor so shaped that a second and lower shoulderis provided, at 22, forhaving squarely abutted thereagainst the loweredge portions of the depending neck of the eyelet, and beyond'the locusof the bottom of the eyelet this shoulder 22" is laterallydownwardlycurvedr into smooth merging with the cylindrical interior wall of thejacket therebelow.

In anyform of the invention. then, due to the factzthat the Kovar memberwelded to the jacket is thereby fused thereto annularly ofthe jacket,

and due to the fact vthat the glass cast against.

the Kovar' member is fused thereto also annularly of the jacket, apermanent gas-tight seal is provided between the jacket andtheinsulator; and due to the fact that theglass likewise is fusedencirclingly of a part of the central electrode made of Kovar, apermanent gas-tight seal is `at the same time provided'between thecentralelectrode and the insulator-all exactly as in the aforesaidpatent to me, but according to a method of manufacture which is verymuch less expensive than that of said 4patent and provides amechanically strong and rugged plug.

It is to be emphasized that while I have stressed herein theadvisability of preassembly of the Kovar member and the jacket, and bywelding, and in such manner that by this preassembly the Kovar member iswholly or partially extended into the interior of the jacket, it ispossible that further experimentation will show that satisfactoryresults'can be obtained when such weld-joined preassembly is dispensedwith', or when the Kovar member is wholly he-v yond one end of thejacket; that is, when the molten glass is to cast to form the insulatorso as to solidify partially against the jacket and partially against theKovar member, and thereafter, with the Kovar'member .only partiallyinserted in the jacket or wholly beyond an end of the same, the Kovarmember is permanently fused to the jacket. As in the aforesaid patent tome stated, the terms fused or fusion" are intendv vention as defined bythe claims.

I claim:

1. A spark-plug comprising a metal jacket, a central electrode includinga length of Kovar, a Kovar member permanently fused to the jacket, and aglass insulator c ast in the jacket and around said electrode length andagainst said member and fused to the two parts last mentioned by thesetting of the glass. 1

2. A spark-plug comprising a metal jacket, a

central electrode including a length of Kovar, a

Kovar member of a composition different from that of the jacket andpermanently fused to the jacket, and a glass insulator cast in thejacket and around said electrode length and against said member andfused to the two parts last mentioned by the setting of the glass.

3. A spark-plug comprising a metal jacket, a central electrode includinga length of Kovar, a Kovar member at least partially extended into theinterior of the jacket and permanently fused to the jacket, and a glassinsulator cast in the against said member and fused to the two partslast mentioned by the setting of the glass.

4. A spark-plug comprising a metal jacket, a central electrodeincluding. a length of Kovar, a Kovar member wholly in, the interior ofthe jacket and permanently fused to the jacket, and

a glass insulator cast in the jacket and around 5; A spark-plugcomprising a metal jacket, said jacket having an interior shoulder, aKovar member permanently fused at said shoulder to the jacket, a centralelectrode, including a length of Kovar, and a glass insulator cast inthe jacket and around said electrode length and against said member andfused to the two parts last mentioned by the setting of the glass.l

6. A spark-plug comprising an electrode including a length of Kovar, ametal jacket open from end to end and through which the-elec.- trodepasses, a Kovar member permanently fused to the jacket, and a solidglass body supporting the electrode and insulating it from the jacket,said glass body fused to said electrode length and to said member. l

7. A spark-plug comprising an electrode, including a length of Kovar, ametal jacket open from end to end and through which the electrodepasses, a Kovar member having a flange, said flange permanently fused tothe jacket, and a solid glass body supporting the electrode andinsulating it from the jacket, said glass body fused to said electrodelength and to said member.

8. A spark-plug comprising an electrode, including a length of Kovar, ametal jacket open from end to end and through which the electrodepasses, a solid glass body supporting the electrode and insulating itfrom the jacket, the metal jacket carrying a thin flange member ofKovar, said flange member being joined to the jacket by permanent fusionof the metal of the flange member with the metal of the jacket, and saidglass body being fused to said electrode length and to said member.

y 9. A spark-plug' comprising an electrode, including a length of Kovar,,a metal jacket open from end to end and through which ythe elec-` larlyshouldered, and said flange is permanently fused to the jacket at saidshoulder:

v12. A spark-plug -as in claim 9, in which the jacket isinternallyannularly shouldered, and

said flange is permanently fused to the jacket at said shoulder, saideyelet including a neck portion depending below said shoulder.

13. A spark-plug as in claim 9, in which intery mediate its ends thejacket has a higher internal annular shoulder and vva lower internalanljacket Aand around said electrode length and 7s nular shoulder, saideyelet including a neck portion dependent from said flange, said angebeing permanently fused to the jacket at said higher shoulder and therim portion at the bottom of said neck overlying said lower shoulder.

14. A spark-plug as in claim 9, in which the jacket is internallyannularly shouldered, and said flange is permanently fused to the jacketat said shoulder, said eyelet including a portion downwardly offset fromsaid flange, and the interior of the chamber being recessed below saidshoulder to receive said downwardly Voiset portion.

15. The method of assembling a spark-plu k,which includes, as one step,casting a solid body of glass about a central electrode, including alength of Kovar, and within a metal jacket and against .a KovarA ring,so that, during the setting ofthe glass to form said body the glass isfused to said electrode length and to said ring, and, as another step,welding the Kovar ring to the jacket.

16. The method of assembling a spark-plug which includes, as one step,:casting a solid body of glass about a central electrode, including alength of-Kovar. and withina metal jacket and against a Kovar ring, sothat, during the setting of the glass to form said body the glass isfused to said electrode'length and to said Iring, and,

as another step, welding the Kovar ring to the jacket before saidcasting step.

17. The method of claim 16, in which said ring includes a 'thin tubularportion open at both ends and through the interior o f which, the moltenglass is ilowed longitudinally of the jacket during said casting, saidtubular portion at one end terminating in an edge directed toward oneend `of the jacket. and said ring being arranged in the jacket, relativetothe point of admission of the molten glass, so that the flowing glassapproaches said edge after passing .through

